Wheel modules include one or more integrated circuits to perform measurement and signal processing tasks required by the system. The integrated circuit is programmed to wake up for less than a second at intervals of typically 10-30 seconds, to perform measurements and transmit data. The rest of the time is spent in the sleep (powerdown) mode, where only a timer circuit is active. Since more than 99% of the time may be spent in sleep mode, the power consumption of the device in this mode is obviously of importance.
When produced in the currently used technologies, such integrated circuits have a maximum limit for the internal supply voltage of the digital core circuits which is less than the voltages provided by the energy sources mentioned above. A voltage regulator or converter is therefore required to adapt the supply voltage to a level that is compatible with the digital core of the integrated circuits.
It is often the case that the integrated circuit includes special higher voltage elements, so that the voltage regulator can be provided on the same chip as the low voltage digital core.
Due to the limited capacity of the power sources, it is important that the power consumption of the wheel module is minimized. Typically, voltage regulators are used for voltage conversion. The voltage regulator requires a certain bias current to operate, and this current constitutes a significant part of the sleep mode power consumption.